**EXHIBIT 31.2**

 

**CERTIFICATIONS**

 

I,Glenn P. Sblendorio, certify that:

 

1.                                       Ihave reviewed this Quarterly Report on Form 10-Q of The Medicines Company;

 

2.                                       Basedon my knowledge, this report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

 

3.                                       Basedon my knowledge, the financial statements, and other financial informationincluded in this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, andfor, the periods presented in this report;

 

4.                                       Theregistrant’s other certifying officer and I are responsible for establishingand maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) and internal control over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant andhave:

 

a)          Designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to be designedunder our supervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which thisreport is being prepared;

 

b)          Designed such internal control overfinancial reporting, or caused such internal control over financial reportingto be designed under our supervision, to provide reasonable assurance regardingthe reliability of financial reporting and the preparation of financialstatements for external purposes in accordance with generally acceptedaccounting principles;

 

c)          Evaluated the effectiveness of theregistrant’s disclosure controls and procedures and presented in this reportour conclusions about the effectiveness of the disclosure controls andprocedures, as of the end of the period covered by this report based on suchevaluation; and

 

d)          Disclosed in thisreport any change in the registrant’s internal control over financial reportingthat occurred during the registrant’s most recent fiscal quarter (theregistrant’s fourth quarter in the case of an annual report) that hasmaterially affected, or is reasonably likely to materially affect, theregistrant’s internal control over financial reporting; and

 

5.                                       Theregistrant’s other certifying officer and I have disclosed, based on our mostrecent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of the registrant’s board ofdirectors (or persons performing the equivalent functions):

 

a)          All significant deficiencies andmaterial weaknesses in the design or operation of internal control overfinancial reporting which are reasonably likely to adversely affect theregistrant’s ability to record, process, summarize and report financialinformation; and

 

b)          Any fraud, whether or not material,that involves management or other employees who have a significant role in theregistrant’s internal control over financial reporting.

 

 
|                                          |   | /s/ Glenn P. Sblendorio                              |
|------------------------------------------|--------|------------------------------------------------------|
| Dated:  November 10, 2008 |   | Glenn P. Sblendorio                                  |
|                                     |   | Executive Vice President and Chief Financial Officer |

 

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